Great Lakes fish consumption advisories: is mercury a concern?

Abstract

The majority of the restrictive fish consumption advisories for the Canadian waters of the Great Lakes issued by the Ontario Ministry of the Environment, Canada based on the most restrictive contaminant, are attributed to polychlorinated biphenyls (PCBs) and dioxins/furans. Mercury currently causes about <1-2.5% and 9-16% of the restrictive advisories for the general population (GP) and sensitive population of children under 15 and women of child-bearing age (SP), respectively (the St. Lawrence River is not considered here). Toxaphene causes minor restrictions. At present it is not clear that if PCBs and dioxins/furans were to decrease below their fish consumption advisory guidelines, current fish mercury levels would replace some, most or all of the consumption restrictions. In order to examine this, location-, species- and size-specific fish consumption advisories were calculated for a "mercury only" scenario by disregarding the presence of the other contaminants. In the absence of other contaminants, mercury would replace some of the current advisories caused by other contaminants; however, the overall advisories would be minimally to moderately restrictive (<1-7% for GP; 13-32% for SP). Almost half of the Great Lake blocks considered here would have more than double the unrestricted consumption advisories than they currently have, with Lake Ontario showing the greatest improvement. Certain size ranges of each species across the main basins of the Canadian waters of the Great Lakes would be deemed safe for unrestricted consumption. However, at least some sizes of a number of species from certain locations of each lake would still have "do not eat" advisories issued for the SP, although these restrictions would be minimal for Lake Erie. These results suggest that the current mercury levels in the Canadian Great Lakes fish are of very minor concern for the GP and of moderate concern for the SP.

Evaluation and Interconversion of Various Indicator PCB Schemes for ∑PCB and Dioxin-Like PCB Toxic Equivalent Levels in Fish

“…Levels of various contaminants have been monitored in Ontario fish since the 1970s through Sport Fish Contaminant Monitoring Program of Ontario Ministry of the Environment and Climate Change (OMOECC). 18 The monitoring data generated by the program include 1151 fish samples measured for 56 PCB congeners. After excluding 112 samples with all major PCB congeners below their detection limits, the final data set included 572 skinless, boneless fillet (SBF) samples of 25 sport fish species from 51 locations, 22 whole body fish composite (WFC) samples of two forage fish species from one location, and 445 young-of-the-year whole body fish composite (YFC) samples of 11 fish species from 60 locations (Supporting Information (SI) Table S1a).…”

Mercury in the Great Lakes region: bioaccumulation, spatiotemporal patterns, ecological risks, and policy

“…Feather mercury concentrations in nestlings declined by nearly 80% from 1989 to 2010, a trend attributed to a lake-level stabilization order by the International Joint Commission that was implemented in 1999. Interestingly, as observed in some fish populations (Monson 2009;Monson et al 2011;Bhavsar et al 2011;Zananski et al 2011), there appears to be a biphasic response in nestling mercury concentrations with increasing concentrations observed over the period spanning 2000-2010.…”

“…Sandheinrich et al (2011) examined the proportion of predatory fish that were predicted to be at risk from high concentrations of mercury and found that most fish at risk were in inland lakes and impoundments, whereas no sites in the Great Lakes had fish exceeding threshold concentrations for adverse effects. Bhavsar et al (2011), who examined consumption advisories in the Canadian waters of the Great Lakes, found that only \1-2.5% of present restrictive advisories for the general population and 9-16% for the sensitive population were due to mercury. If other contaminants were not a factor, mercury in fishes from Canadian waters of the Great Lakes was considered to be of minor concern for the general population and of moderate concern for sensitive populations.…”

The Risk of Mercury Exposure to the People Consuming Fish from Lake Phewa, Nepal

“…However, the same person can consume only 2.7, 1.5 and 0.9 kg of the respective fishes per week to not exceed the 0.7 µg/kg body weight limit proposed by the US-NCR. The government should be responsible for obtaining information on the availability and contaminant levels for commonly eaten fish species so as to allow people to make informed decisions about the health risks from fish consumption [16,28]. Sometimes the people are compelled to choose chemical risk rather than giving up the consumption of contaminated fish due to their cultural and religious beliefs [25].…”

“…Since the main susceptible groups for Hg poisoning are growing fetus and growing children ( i.e ., undergoing brain development), women of reproductive age and small children are regarded as the most susceptible targets to Hg poisoning [15,16,17,18,19]. It has been proven that Hg is bound to proteins such as muscle, which is the main edible part of fishes, and its levels there cannot be reduced or removed by cooking [20].…”